Fires or explosions can result when ignition sources—such as sparks, embers, hot process material, or bits of heated metal—are found within closed containers. Dust explosions and fires, for example, are relatively common in various industries. To create such an explosion, an ignition source causes a fuel, like fine dust particles, dispersed in a container to explode. Dust explosions can occur in a variety of containers, including dust collectors, air filters, pneumatic conveyors, ducts, pipelines, and other confined spaces commonly encountered in industrial sites.
Ignition sources may result from, for example, industrial or manufacturing processes occurring at the location of the fire or explosion. Abrasive grinding, cutting, welding operations, and electrostatic discharge, among many others, may result in sparks or embers capable of igniting suspended particles in a container.
Ignition sources may result from material handling systems, such as conveyors, which may be enclosed or open to the atmosphere moving bulk material that may contain hot material from one process to a storage point.
Conventional ignition-source detecting systems typically employ one or more detectors connected to a centralized control unit, located, for example, in a manufacturing facility's control room. The control unit typically is connected to one or more valves for controlling the release of water, carbon dioxide, another fluid intended to prevent ignition, or another safety mechanism such as a diverter valve.
Conventional ignition-source detection systems typically use a combined controller and monitor with hard wiring running from each detector and spray nozzle (or other device) back to this combined unit. Such systems have a limited capacity regarding how many applications of ignition-source detection activity they can support. Frequently, the limited number of connection points included in conventional ignition-source detection hardware limits the ability to add ignition-source detection points to a process. When this occurs, the combined controller and monitor must be replaced with a larger capacity unit or a separate independent system. Either way, the combined controller and monitor limits flexibility. Typically, conventional ignition-source detection systems are limited to between four and sixteen detection and extinguishing points.
Running the wires necessary to connect the detectors to the control unit is costly. Moreover, electromagnetic radiation, temperature differences, and other factors may jeopardize communications between the control unit and the attached sensors and spray nozzles. Accordingly, testing and maintenance of the wires is needed to ensure the proper functioning of the ignition-source detecting system. The wires necessitated by such conventional systems are costly to install, test, and maintain.
The control units of conventional ignition-source detecting systems depend on mechanical or solid state relays to identify and counteract ignition sources in containers. To change or customize such a control unit requires rewiring its constituent components. Accordingly, the rigid electrical design of conventional ignition-source detecting systems hampers customization and leads to increased expense and reduced flexibility of application.
In conventional ignition-source detecting systems, the control unit is disposed at a location remote from the container being monitored. Typically, the control unit resides in a climate-controlled location to prevent exposure to fluctuating temperatures and dusty conditions. For example, conventional ignition-source detection systems typically require the combined controller and monitor to be in a lower hazard level dusty environment, such as ATEX Zone 22, Class 2 Division 2 or unrated environment.
Typically, a single combined controller and monitor is attached to conventional ignition-source detecting systems. This forces all control and monitoring activity to take place in one location, typically located far from the monitored container.
In cold climates where water is used to prevent ignition, conventional ignition-source detecting systems include a heat tracing circuit to ensure that the water does not freeze. Such heat tracing circuits typically employ electricity to generate necessary heat. Conventionally, ignition-source detecting systems do not monitor the supply of electricity to such heat tracing circuits.
The detectors included in conventional ignition-source detecting systems are not capable of creating a direct digital signal in response to observed infrared radiation. Accordingly, such detectors either output an analog signal or require an analog-to-digital converter to communicate with digital control systems. An analog signal may output a variable voltage or current in response to the level of radiation detected. The analog output must then be interpreted by a controller to determine an appropriate system response.
Detectors in conventional ignition-source detecting systems typically are not configured to detect flames. Instead, conventional systems focus on detecting sparks and embers only. Flame detection has historically been tackled in a manner different than the detection of sparks and embers. To the extent that conventional ignition-source detecting systems detect flames as well as sparks and embers, they include separate detectors for detecting flames and for detecting other ignition sources.
Conventional detectors do not allow for sensitivity adjustment. They either require calibration prior to installation or cannot be adjusted at all. It is desirable to allow sensitivity adjustment before, after, or during use or installation.
It is desirable to provide systems and methods for enhancing conventional ignition-source detection systems to overcome the limitations described above.